Emiliano Grillo charged into a four-stroke lead before the second round of the Mayakoba Golf Classic was suspended due to darkness on Friday.
The Argentinian carded an eight-under 63 at the El Camaleon Golf Club in Playa del Carmen in Mexico, where Brooks Koepka and Rickie Fowler struggled, to move into 13 under.
Grillo, whose only win on the PGA Tour came in 2015, is four shots ahead of Tom Hoge (67) and Tony Finau (66).
After a difficult start to 2020 saw him miss the cut at eight of his first 13 tournaments, to go with a disqualification at the Arnold Palmer Invitational, Grillo has found some better form later in the year.
He mixed nine birdies with one bogey in the second round, which was delayed by an hour due to inclement weather and later suspended because of darkness.
A pleasant surprise for @GrilloEmiliano. pic.twitter.com/qBNxqSBbJN
— PGA TOUR (@PGATOUR) December 4, 2020
Only 18 players were yet to finish their second rounds, with Andy Ogletree the best-placed, the American – who is making his professional debut – sitting at seven under through 15 holes.
Hoge and Finau are Grillo's nearest challengers, while overnight leader Russell Knox is at eight under after shooting a 69.
Joel Dahmen (67), Aaron Wise (68) and Kyle Stanley (67) are in the group alongside Ogletree in a tie for fifth.
Coming off a win at the Houston Open and a runner-up finish at the Mayakoba Golf Classic last year, Carlos Ortiz (69) is at six under, tied for ninth with eight others.
World number three Justin Thomas bounced back with a 67 to get to three under, sitting in a tie for 34th.
However, Koepka (71) and Fowler (72) are projected to miss the cut after getting to even par – one shot adrift of making the weekend with the second round yet to be completed.